[PATCH 3.19 058/101] iio: core: Fix double free.

Greg Kroah-Hartman
2015-04-17T13:36:22Z

From: Martin Fuzzey <mfuzzey@parkeon.com>

commit c1b03ab5e886760bdd38c9c7a27af149046ffe01 upstream.

When an error occurred during event registration memory was freed twice
resulting in kernel memory corruption and a crash in unrelated code.

The problem was caused by
iio_device_unregister_eventset()
iio_device_unregister_sysfs()

being called twice, once on the error path and then
again via iio_dev_release().

Fix this by making these two functions idempotent so they
may be called multiple times.

The problem was observed before applying
78b33216 iio:core: Handle error when mask type is not separate

Signed-off-by: Martin Fuzzey <mfuzzey@parkeon.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/iio/industrialio-core.c | 5 +++--
drivers/iio/industrialio-event.c | 1 +
2 files changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -832,8 +832,7 @@ static int iio_device_add_channel_sysfs(
* @attr_list: List of IIO device attributes
*
* This function frees the memory allocated for each of the IIO device
- * attributes in the list. Note: if you want to reuse the list after calling
- * this function you have to reinitialize it using INIT_LIST_HEAD().
+ * attributes in the list.
*/
void iio_free_chan_devattr_list(struct list_head *attr_list)
{
@@ -841,6 +840,7 @@ void iio_free_chan_devattr_list(struct l

list_for_each_entry_safe(p, n, attr_list, l) {
kfree(p->dev_attr.attr.name);
+ list_del(&p->l);
kfree(p);
}
}
@@ -921,6 +921,7 @@ static void iio_device_unregister_sysfs(

iio_free_chan_devattr_list(&indio_dev->channel_attr_list);
kfree(indio_dev->chan_attr_group.attrs);
+ indio_dev->chan_attr_group.attrs = NULL;
}

static void iio_dev_release(struct device *device)
--- a/drivers/iio/industrialio-event.c
+++ b/drivers/iio/industrialio-event.c
@@ -493,6 +493,7 @@ int iio_device_register_eventset(struct
error_free_setup_event_lines:
iio_free_chan_devattr_list(&indio_dev->event_interface->dev_attr_list);
kfree(indio_dev->event_interface);
+ indio_dev->event_interface = NULL;
return ret;
}